Marine Weather and Tide Forecast for Sullivan,s Island, SC

NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
A surface low will continue to develop north of the region and offshore under a stronger shortwave, with surface high pressure building behind it. This will result in a dry conditions locally, with a heightened surface pressure gradient resulting in slightly breezy conditions along the coast where gusts into the teens are expected to continue into the overnight period. Ahead of surface high pressure, cooler air is expected to advect south into the region while stratus begins to erode due to a substantial amount of dry air aloft. The setup is likely to lead to noticeably colder temps than the previous night, with overnight lows generally in the upper 20s/lower 30s inland to lower/middle 30s near the coast.
These temps combined with breezy coastal winds could produce wind chills into the low-upper 20s, lowest in the Tri-County Area.

SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/
The Tuesday through Thursday period will offer much improved conditions compared to the rainy and foggy weather that has been observed for the past several days. A broad west to northwest flow will dominate aloft as a large area of high pressure pressure gradually shifts offshore of the Southeast U.S. coast. A broad trough is forecast to dig across the eastern CONUS Wednesday into Thursday which will help drive a weak cold front offshore Thursday night. Moisture return ahead of the front looks meager at best with a dir airmass progged to hold over much of the Gulf. PWATs are forecast to surge somewhat right ahead of the front itself, but will remain well below the 1" mark. This lack of moisture coupled with the corridor of great quasi-geostrophic forcing progged to remain displaced well to the north, suggests the front will pass through dry with little prospects for measurable rainfall. Temperatures will moderate ahead of the front with highs reaching the upper 40s/lower 50s Tuesday and lower-mid 60s Wednesday into Thursday. Lows Wednesday morning will drop into the upper 20s well inland to the lower 40s at the beaches with upper 30s/lower 40s inland with upper 40s/near 50 at the beaches Thursday morning.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
Quiet weather will generally prevail into the weekend as high pressure slides east across the Southeast U.S. and eventually offshore. A cold front is forecast to backdoor in from the north on Sunday as as the beginnings of a cold air damming/wedge take shape.
There are considerable timing differences noted with the southward moving wedge front Sunday. The timing of the front will closely tied to any possible surface cyclone that develops along the front. For now, both the GFS and ECMWF ensembles, including any AI counterparts, keep any surface low weak and tracking well to the north. The area may be fully wedged in on Monday with cloudy and cool conditions prevailing. There was no reason to deviate from the 08/13z NBM at this time given the uncertainty, although NBM-based temperatures Sunday and Monday may end up being too warm depending on how the wedge evolves.

AVIATION /00Z TUESDAY THROUGH SATURDAY/
MVFR cigs will prevail at CHS/JZI terminals this evening and overnight, primarily through about 13Z Tuesday. A brief window for IFR cigs is possible at CHS/JZI terminals overnight as well, but guidance has trended higher and dry air filtering into the region from the west should eventually erode cloud cover near or shortly after daybreak Tuesday. VFR conditions are then expected at CHS/JZI terminals through 00Z Wednesday. At SAV, MVFR cigs should prevail for the next few hours, but clouds begin to erode earlier, thus have indicated a transition to TEMPO MVFR cigs between 01Z-03Z tonight.
There is a risk for MVFR cigs to temporarily impact the SAV later tonight, but confidence remains too low to include in the latest TAF issuance. VFR conditions should prevail at SAV during the second half of the night through 00Z Wednesday.

Extended Aviation Outlook: There are no high confidence concerns.

MARINE
Tonight: Northerly winds gusting up to 15-20 kt early evening will strengthen further overnight into early morning hours, resulting in gusts around 25 kt, highest in the nearshore waters from South Santee down to Edisto Beach, SC, and in the outer Georgia waters from Savannah to Altamaha Sound. Seas will also build to 4-6 ft, largest across the outer reaches of the nearshore waters from South Santee down to Edisto Beach, SC and across the outer Georgia waters from Savannah to Altamaha Sound tonight. Small Craft Advisories will therefore remain in effect for these marine zones (AMZ350 and AMZ374) through the night.

Tuesday through Saturday: Winds and seas will diminish below advisory levels across the South Santee-Edisto Beach nearshore and Georgia offshore waters by mid-morning Tuesday. Otherwise, winds will turn more southerly for Wednesday and more westerly Thursday into Saturday as high pressure slides offshore and a cold front pushes offshore. Winds and seas could surge to Small Craft Advisory levels Wednesday night/Thursday morning immediately ahead and just behind the cold front. Advisories at the most likely over the South Santee-Edisto Beach and the Georgia offshore legs where the latest LREF probs for gusts >25 kt is running 50-80%. Otherwise, winds and seas will remain below Small Craft Advisory thresholds.

CHS WATCHES/WARNINGS/ADVISORIES
GA...None.
SC...None.
MARINE...Small Craft Advisory until 10 AM EST Tuesday for AMZ350-374.